I think I was told by a friend that lead acid batteries are 30 % efficient . He was a financial man which sometime is better than a scientist . His job was to advise people about the realities of industries they would invest in . I have always thought that estimate a bit low .
Graphite or graphene on paper as capacitors ? I say paper as it is easy to do and has respectable dielectric constant . My feeling is the coating is unimportant in audio applications . The next step is to add an electrolyte , surely that puts an end to any supposed sonic advantages ? Silver might just be better as it will lend itself to termination more easily . I seem to remember Philips used lead foil for their polystyrene caps to promote better termination and reliability . If you have a radio that is intermittent put it in a freezer bag in the freezer . Often that will find a defective polystyrene cap ( use your fingers to warm them up ) . GOC/NPO ceramics often will as a substitute , sometimes preferable .
Graphite or graphene on paper as capacitors ? I say paper as it is easy to do and has respectable dielectric constant . My feeling is the coating is unimportant in audio applications . The next step is to add an electrolyte , surely that puts an end to any supposed sonic advantages ? Silver might just be better as it will lend itself to termination more easily . I seem to remember Philips used lead foil for their polystyrene caps to promote better termination and reliability . If you have a radio that is intermittent put it in a freezer bag in the freezer . Often that will find a defective polystyrene cap ( use your fingers to warm them up ) . GOC/NPO ceramics often will as a substitute , sometimes preferable .
An externally hosted image should be here but it was not working when we last tested it.
This is an old all NPN op amp . I am tempted one day to build it . I think I saw an all NPN power amp once . OK , 1001 reasons not to bother , still interesting . I like the double LTP and how it clamps the input stage ( 2 LTP base voltages ) . Simple and effective .
Point No 5 probably wasn't taken off exactly as drawn . Better at the node point . +/- 6V seems usually low . I imagine BC 550 C worth trying and 1N4148 .
It seems the real MC1530 was slightly more conventional in it's pin out . +/- 9 V and doing somethings better than LM741 which came later . Less components also . Compensation was external .
Linear Integrated Circuits - D Choudhury Roy - Google Books.
Hi DVV . I thought the history of op amps worth showing .In many ways this is far more involved than many amps I see . Because we can have resistor and capacitors plus loads of room we avoid much complexity in power amps . If people bother to read the circuit description it is surprisingly good at what it sets out to do . OK even perhaps the LM358 ( 324 ) betters it now ? That's not the point . There are little tricks used which are still not common in power amp design .
All NPN intrigues me . I wonder sometimes if PNP's make us lazy ? The circuit I just finished must have PNP . It isn't audio . When using valves I use PNP's as they do what no valve can do . It is amazing how many valve builders wouldn't even consider it because it is a transistor . In certain situations it is a shortcut to excellence . Mostly as benign as a resistor when I use a PNP with valves .
I put the MC 1530 up as a Missing Link so to speak . I often wonder if DNA and evolution is a good story ? To me like Alchemy perhaps they are the right ideas with primitive explanations . Too many leaps of the story stated as facts . It is engineering that says this to me and no other thing . I mean no reference to a theist or atheist explanation , I am glad in audio we don't have to guess at what really happened . For that reason we should know a little of how we got where we are .
All NPN intrigues me . I wonder sometimes if PNP's make us lazy ? The circuit I just finished must have PNP . It isn't audio . When using valves I use PNP's as they do what no valve can do . It is amazing how many valve builders wouldn't even consider it because it is a transistor . In certain situations it is a shortcut to excellence . Mostly as benign as a resistor when I use a PNP with valves .
I put the MC 1530 up as a Missing Link so to speak . I often wonder if DNA and evolution is a good story ? To me like Alchemy perhaps they are the right ideas with primitive explanations . Too many leaps of the story stated as facts . It is engineering that says this to me and no other thing . I mean no reference to a theist or atheist explanation , I am glad in audio we don't have to guess at what really happened . For that reason we should know a little of how we got where we are .
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This is an extract I read about MC1530 .
My very first OpAmp design, MC1530/31, circa 1963-64, had 6V/us
slew-rate
But it required external compensation.
And it's still being sold, 48 years later...
Obsolete Semiconductors and Electronic Component Part Search - Lansdale Semiconductor | The leader in Semiconductor Manufacturing
I've even had inquiries to re-design it on a modern process
...Jim Thompson
Forgot another bragging point for the MC1530/31... sliding-class-A
output stage... no cross-over distortion ;-)
...Jim Thompson
I found your PDF on it here:
http://www.analog-innovations.com/SED/MC1530-TeachingExercise.pdf
I'm not sure how increasing the emitter areas of the output transistors implements the sliding class A.
Without any PNPs for current source loads it must have taken some intuition to arrange things so that everything canceled out and left the output at zero volts!
.
If the output stage does work as stated it is worth looking at . 6 V / is not too bad for something which eventually ran off of 18 V ( was 12 ) . It's gain is approximately 60 x 30 x 5 .
Re: LM324 and crossover distortion
My very first OpAmp design, MC1530/31, circa 1963-64, had 6V/us
slew-rate
But it required external compensation.And it's still being sold, 48 years later...
Obsolete Semiconductors and Electronic Component Part Search - Lansdale Semiconductor | The leader in Semiconductor Manufacturing
I've even had inquiries to re-design it on a modern process
...Jim Thompson
Forgot another bragging point for the MC1530/31... sliding-class-A
output stage... no cross-over distortion ;-)
...Jim Thompson
I found your PDF on it here:
http://www.analog-innovations.com/SED/MC1530-TeachingExercise.pdf
I'm not sure how increasing the emitter areas of the output transistors implements the sliding class A.
Without any PNPs for current source loads it must have taken some intuition to arrange things so that everything canceled out and left the output at zero volts!
.
If the output stage does work as stated it is worth looking at . 6 V / is not too bad for something which eventually ran off of 18 V ( was 12 ) . It's gain is approximately 60 x 30 x 5 .
Re: LM324 and crossover distortion
Interesting link sent to me ( thanks Martina ) . If using Quad ESL I see no reason to think it wouldn't be a winner ( damping factor ) . I would build it in it's simplest form as beyond that a conventional amp makes more sense . Interesting to see a silicon device look so much like a triode . Nelson Pass , that should be enough to get some interested .
http://www.firstwatt.com/pdf/art_f6_baf.pdf
http://www.firstwatt.com/pdf/art_f6_baf.pdf
Nige, your ability to do at least most of it, if not all, is not in question.
Try as hard as I might, I fail to comprehend the ultimate point of it all.
Call me extreme, but I firmly belive and live by the old AR advertising leaflet from the early 70ies, in which they said that a loudspeaker which is great with classical music but not so good with pop/rock, and vice cersa, are both poor speakers; a good speaker should sound good with anything.
So it is with amps as well, I am convinced - no doubt you could construct a dedicated amp for say Quad electrostatics, but an amp which would not sound very good with some other speaker. To me, that is a flawed amp. I realize that making an amp highly load tolerant is no peanuts, it takes work, materials an money, and there's no way under the sun that it will sound exactly the same with all speakers, but we can get the sound differences to say small, even insignificantly small.
So, if I were you, I'd be thinking about an amp of reasonable power, capable of doing its best with just about anything someone has named a speaker and doesn't cost an arm and a leg in the process.
Try as hard as I might, I fail to comprehend the ultimate point of it all.
Call me extreme, but I firmly belive and live by the old AR advertising leaflet from the early 70ies, in which they said that a loudspeaker which is great with classical music but not so good with pop/rock, and vice cersa, are both poor speakers; a good speaker should sound good with anything.
So it is with amps as well, I am convinced - no doubt you could construct a dedicated amp for say Quad electrostatics, but an amp which would not sound very good with some other speaker. To me, that is a flawed amp. I realize that making an amp highly load tolerant is no peanuts, it takes work, materials an money, and there's no way under the sun that it will sound exactly the same with all speakers, but we can get the sound differences to say small, even insignificantly small.
So, if I were you, I'd be thinking about an amp of reasonable power, capable of doing its best with just about anything someone has named a speaker and doesn't cost an arm and a leg in the process.
A small diversion - tonight, despite a shearing icy wind, Belgrade is full of kilts. There are about 3,000 Scots here tonight, to watch the Scotland-Serbia football match tomorrow. And it's just a friendly game, since both teams are out of the next world championship.
I spotted MacLeod, Campbell and a few other known to me clan colours. I admit to being partial to the Scots, the several I knew were excelent people, and my visit to Scotland in 2009 was a true pleasure not often enjoyed. I feel Scotland is a place I could live in easily and comfortably, despite the foul weather.
I spotted MacLeod, Campbell and a few other known to me clan colours. I admit to being partial to the Scots, the several I knew were excelent people, and my visit to Scotland in 2009 was a true pleasure not often enjoyed. I feel Scotland is a place I could live in easily and comfortably, despite the foul weather.
The point is fundamental engineering . We at last have a reasonably linear output stage . That has to be a good point to start from . One thing I think I never got across is what Bob Stuart was saying years ago . Every time we process the signal through another stage of an amplifier it is a copy . If we define what we need as a minimum standard we should work towards that goal and seek simplicity . Everything else is a caprice . A noble one no doubt ?
Equally an amp like this one of Nelson Pass is a caprice also ?
The point that came through was if the output stage has spare current it can power the feedback loop . I don't know if it is accident or not , he comes up with what was said to be the ideal damping factor of 16 . Beyond that thick cables matter most ( or 3 wire to include speaker terminal feedback ) . The transformer he uses has op amp distrotion levels and is cheap .
We now have an amp where a feedback volume control is likely to work very well . Thus the quieter we run the better everything gets . That usually is not true of modern amps . No volume control between pre amp and power . That has to be a good idea ?
In both Germany and UK Jet engines were not taken seriously . In 1927 they were already becoming realistic devices . Both rockets and jets are simple devices , and it harms them how ?
I noticed recently that the KEF LS 50 speaker has below 1 % distortion . As long as an amp has minimal crossover distortion and reasonable damping factor the 1947 standard of hi fi is still more than good enough ( 0.1 % ) . There " should " be no human on the planet able to say differently ?
Equally an amp like this one of Nelson Pass is a caprice also ?
The point that came through was if the output stage has spare current it can power the feedback loop . I don't know if it is accident or not , he comes up with what was said to be the ideal damping factor of 16 . Beyond that thick cables matter most ( or 3 wire to include speaker terminal feedback ) . The transformer he uses has op amp distrotion levels and is cheap .
We now have an amp where a feedback volume control is likely to work very well . Thus the quieter we run the better everything gets . That usually is not true of modern amps . No volume control between pre amp and power . That has to be a good idea ?
In both Germany and UK Jet engines were not taken seriously . In 1927 they were already becoming realistic devices . Both rockets and jets are simple devices , and it harms them how ?
I noticed recently that the KEF LS 50 speaker has below 1 % distortion . As long as an amp has minimal crossover distortion and reasonable damping factor the 1947 standard of hi fi is still more than good enough ( 0.1 % ) . There " should " be no human on the planet able to say differently ?
Am I to understand from the above that it's really just art for art's sake? Just an engineering exercise?
Fine, I can understand that we all sometimes just go silly for the fun of it, or because we're simply curious. I cannot deny that I also do this when I have some free time on my hands, which is very rare unfortunately.
But, if so, why build a whole therory around it?
Exactly what do we gain by making an amp all NPN? And why should we do that, in this day and age, when we have rather good matching PNPs?
Fine, I can understand that we all sometimes just go silly for the fun of it, or because we're simply curious. I cannot deny that I also do this when I have some free time on my hands, which is very rare unfortunately.
But, if so, why build a whole therory around it?
Exactly what do we gain by making an amp all NPN? And why should we do that, in this day and age, when we have rather good matching PNPs?
The change from valves to transistors was accompanied by much discussion about the quality of distortion. Conventional wisdom appears to be that the distortion of early transistor amps was more intrusive, or at least less acceptable. Once quality enters the argument, it can go on forever.
I can see a good reason to build old designs if they are representative of the best practice of a particular period. Exploring a path that history escaped from at the earliest opportunity seems a bit far out even for a hobby. The possibilities are endless...
It's an interesting question though. Where would we be without PNP?
The point is we lost a lot over the years . Bootstrapping almost abandoned . Here is a conventional feedback amplifier . Except it is far from conventional . The transformer I find has undreamt of performance . The idea of using the transformer as if it was a gain stage is very clever . The output stage as in bootstrapping provides the power to drive the circuit . The big downfall of this circuit is the availability of the output devices I beleive . I have some very disgusting fet's and a mains transformer . See how far I get .
All NPN , it is always worth considering . The op amp I gave ( MC 1530 ) is I feel worth trying as a power amp . It looks to me to be a recipe for good performance , especially if the sliding bias can be made to work at amps rather than mA . Somewhere he claims GBP of 10 MHz , 33 V / uS when carefully compensated ( better than LM 301 if so ) . A dinosaur with attitude ? Even the output voltage is OK . Most modern op amps don't go high enough to claim so much more . With some 2N4403 as inputs it probably would be OK as a phono stage ? As far as I know NPN in chip form is far easier . Thus even today it is the device of choice . PNP usually gives low noise .
I have some work to finish so the above is one day perhaps . I hope to knock a TDA 2040 into class A for fun soon . If in the unlikely event it survives I will post the distortion if worth knowing . I hope to run 1.25 A .
All NPN , it is always worth considering . The op amp I gave ( MC 1530 ) is I feel worth trying as a power amp . It looks to me to be a recipe for good performance , especially if the sliding bias can be made to work at amps rather than mA . Somewhere he claims GBP of 10 MHz , 33 V / uS when carefully compensated ( better than LM 301 if so ) . A dinosaur with attitude ? Even the output voltage is OK . Most modern op amps don't go high enough to claim so much more . With some 2N4403 as inputs it probably would be OK as a phono stage ? As far as I know NPN in chip form is far easier . Thus even today it is the device of choice . PNP usually gives low noise .
I have some work to finish so the above is one day perhaps . I hope to knock a TDA 2040 into class A for fun soon . If in the unlikely event it survives I will post the distortion if worth knowing . I hope to run 1.25 A .
BTW . The folk law about older amps is mostly untrue . 99% untrue if designs which passed the scrutiny of the technical magazines . The Leak stereo 30 for example . Harold Leak made fabulous valve amps . In fact his was the first mass production hi fi amp in 1947 ( I gave one away , yikes ) . Crossover distortion was troublesome as was too little current in the input to the VAS in early transistor amps . However Leak was dogged in making sure his class AB amps were reasonably identical to the previous designs . This was done with live verse hi fi demonstrations and included the previous amps . I became addicted to hi fi through Leak transistor amps . I don't think hearing the very best amps in the world was as big a leap as hearing the Leak Delta 30 . Even the Germanium versions pass muster . Most of the amps ever sold were rubbish , the valve ones especailly ( hum , hiss , distortion , explosions ) .
Google Image Result for http://obrazki.elektroda.net/65_1283442944.gif
These are the sort of amplifiers people think of when talking of the bad old days . My friend John singles them out as his pet hate .
Google Image Result for http://obrazki.elektroda.net/65_1283442944.gif
These are the sort of amplifiers people think of when talking of the bad old days . My friend John singles them out as his pet hate .
We'd pursue designs that favor balanced topologies, probably. Even without using transformers an all-NPN restriction can still permit a lot of variety.
The one strange thing I see is this .What would be standard practice for valve designers is the plague to transistor designers and vice versa . Valve amps do not respond well to vast amounts of feedback , they get ugly for want of a better way to say it . It also makes them more expensive for no good reason . Transistor amps seem to tolerate almost any amount of feedback as long as the rules are followed . The temptation is to go where it goes and add parts . I would say it is much harder to go the other way . Have a goal in mind and see how economically it can be done . I remember seeing old Norton single cylinder 500 racing against the Yamaha TZ 350 two strokes . The Norton was not left for dead . I had a friend who worked on them . He said it is a seriously fast motorcycle . They made replica motors so as to allow the preserved Norton's to race . Simplicity with high performance is a joy to behold .
Although I never had this conversation I suspect Bob Stuart was saying this . When a feedback loop is closed we have no real notion of what harm is being done to the signal inside the amp , in 1980 especailly . Bob's suggestion was although undetectable by usual measurements the copying of the signal must be not the best thing that ever happened to it .
I said something previously that was not uniquely true . I said the Pass amplifier used the output stage to supply current for the feedback loop . Well that is always true . This time I feel the significance was rammed home to me .
Here is a design at the point when it worked . A voltage doubler PSU was added later to get better output ( driver ) . It was disliked and used at below rail voltage as a clean supply ( rail - 2 V ) . Note how ridiculously small the bootstrap is ( 2 u 2 ) . The point is , it was enough . 10 uF was then used as a small increase in distortion could be see at 1 kHz ( not below or above ) . The point is the loop gain of the amp was enough up to 1 kHz . None of what you see was for other than for me to read , it's just my notes . It is a mixture of designs I like , Hitachi , Leak ,JLH . The output into 3 R was great ( goes into AB ) . The output capacitor ( 4 x 1000 uF non polar ) was so as to be certain it was OK for DC offset , I never had a problem . The MOSFET's were marginally inferior to a complimentary feedback pair . The difference was by deduction cured . The 50 kHz graph was the design goal . All graphs were identical down to far below one watt . Note the biasing of capacitors . < 400 mV would be ideal . The transformer in the Pass design usefully avoids that . I had no J Fet to try .
Note there is no significant distrotion of any kind . OPA 604 with complimentary feedback pairs was marginally inferior in measurements and sound . What I suspect is buffering an op amp is not 100 % what one would hope for . It was close run . One criticism , 0.7 A is above the optimum for this FET ( 0.1 A ) . It is OK . An A/AB bias resistor ( < 470 R ) would have been interesting for listening tests . I suspect AB would be more punchy ?
Although I never had this conversation I suspect Bob Stuart was saying this . When a feedback loop is closed we have no real notion of what harm is being done to the signal inside the amp , in 1980 especailly . Bob's suggestion was although undetectable by usual measurements the copying of the signal must be not the best thing that ever happened to it .
I said something previously that was not uniquely true . I said the Pass amplifier used the output stage to supply current for the feedback loop . Well that is always true . This time I feel the significance was rammed home to me .
Here is a design at the point when it worked . A voltage doubler PSU was added later to get better output ( driver ) . It was disliked and used at below rail voltage as a clean supply ( rail - 2 V ) . Note how ridiculously small the bootstrap is ( 2 u 2 ) . The point is , it was enough . 10 uF was then used as a small increase in distortion could be see at 1 kHz ( not below or above ) . The point is the loop gain of the amp was enough up to 1 kHz . None of what you see was for other than for me to read , it's just my notes . It is a mixture of designs I like , Hitachi , Leak ,JLH . The output into 3 R was great ( goes into AB ) . The output capacitor ( 4 x 1000 uF non polar ) was so as to be certain it was OK for DC offset , I never had a problem . The MOSFET's were marginally inferior to a complimentary feedback pair . The difference was by deduction cured . The 50 kHz graph was the design goal . All graphs were identical down to far below one watt . Note the biasing of capacitors . < 400 mV would be ideal . The transformer in the Pass design usefully avoids that . I had no J Fet to try .
Note there is no significant distrotion of any kind . OPA 604 with complimentary feedback pairs was marginally inferior in measurements and sound . What I suspect is buffering an op amp is not 100 % what one would hope for . It was close run . One criticism , 0.7 A is above the optimum for this FET ( 0.1 A ) . It is OK . An A/AB bias resistor ( < 470 R ) would have been interesting for listening tests . I suspect AB would be more punchy ?
In my view, each and every capacitor is a can of worms. The best one is the one which isn't there, especially at the output of an amp.
For the wold of me, I cannot see why are you even thinking about output caoacitors, Nige, and I don't know anyone else who's doing the same. I admit I love some vintage products, but even I look only at direct coupled DC designs. Which, BTW, do not necessarily demand DC Servo ciruits for pure DC operation - see Marantz 170 DC, 1152 DC, 1180 DC, etc schematics, to mention just one manufacturer.
Unless one is absolutely crazy for capacitor induced phase shifts.
For the wold of me, I cannot see why are you even thinking about output caoacitors, Nige, and I don't know anyone else who's doing the same. I admit I love some vintage products, but even I look only at direct coupled DC designs. Which, BTW, do not necessarily demand DC Servo ciruits for pure DC operation - see Marantz 170 DC, 1152 DC, 1180 DC, etc schematics, to mention just one manufacturer.
Unless one is absolutely crazy for capacitor induced phase shifts.
I think I said before , the capacitor is simply so as not to loose the experiment during tests . Interestingly the least obvious sound impediment was the output capacitor . I couldn't measure any real distortion from it . Most of my listening was done without it . If you look it is a non polar cap . If wanting a cap I would have used the old style PSU .
The amp started as a speculation about repairing a stack of Leak Germanium amps . I decided to build something new so as to know as much as I could . The FET's almost mimic the Germanium's in many ways apart from speed . If I remember correctly the Leak Stereo 20 was TO3's on a bracket . So just a simple rewire and resistor bias ( get rid of Darlington half ) .
I learned a lot from this .
1 / I don't like single VAS for it's lack of symmetry . No amount of current fed into the VAS cures it . 10 kHz is OK . Maybe this is why we see the need for ridiculous slewing rates ? A one legged cyclist always has difficulty .
2 / Single input stage is not obviously more stable ( folk law ) , those of the past that were had high capacitance transistors . If a BD139 is substituted then perhaps no VAS cap needed ( it worked with considerably more distortion above 10 kHz ) .
3 / Playing with the VAS emitter resistor can reduce distortion !!! My best guess is the impedance matching to the input is better . If so it will show up as IM distortion . A high gain transistor was not the complete cure ( about trans-conductance ) . 16 R seems a good choice here . This is not simple local feedback as many think . It is usually a trans-impedance stage ( I in V out ) . If you every have tried to use a pre amp with a high output impedance you will know it is not the best idea you ever had . Especially if it almost matches the next stage ( higher can work ) . So why do people assume it is OK here ? I know the arguments and have to agree that many amps designed this way are fine . I just suspect what I have done here is worth a thought . Note 0R was the design goal . 47 R was to hand . It was the first time the 50 kHz distortion was better than perfect ( < 0.1 % ) .
4/ If class AB is mostly A then the application of feedback is easier . This amp will pump current as it then in class AB when loud . 8 mA will drive at least 3 sets of outputs on real music .
5 / I like long tail pair input as it makes life easy . Apart from that a single looks better . Such distortion as it as is harmless enough and invisible in this test .
6 / A complimentary feedback pair input for the very pedantic would be the optimum input . Very low distortion and noise . Slightly better stability . As I like double VAS I think LTP is a no brainer .
I am told that in 1938 Edward Turner by using a bit of thought managed to make a twin cylinder motorcycle for the price of a single , it saved the company . Although plenty of things were wrong with it ( balance factors , no centre support ) , it came to be the one to clone . I feel my amp I show although fundamentally excellent ( that is praise of it and not of myself ) is stupidly simple . A caprice . What I show previously in the MC1530 is better than 90% of what I see . How it accepts feedback especially . Well done J T .
The amp started as a speculation about repairing a stack of Leak Germanium amps . I decided to build something new so as to know as much as I could . The FET's almost mimic the Germanium's in many ways apart from speed . If I remember correctly the Leak Stereo 20 was TO3's on a bracket . So just a simple rewire and resistor bias ( get rid of Darlington half ) .
I learned a lot from this .
1 / I don't like single VAS for it's lack of symmetry . No amount of current fed into the VAS cures it . 10 kHz is OK . Maybe this is why we see the need for ridiculous slewing rates ? A one legged cyclist always has difficulty .
2 / Single input stage is not obviously more stable ( folk law ) , those of the past that were had high capacitance transistors . If a BD139 is substituted then perhaps no VAS cap needed ( it worked with considerably more distortion above 10 kHz ) .
3 / Playing with the VAS emitter resistor can reduce distortion !!! My best guess is the impedance matching to the input is better . If so it will show up as IM distortion . A high gain transistor was not the complete cure ( about trans-conductance ) . 16 R seems a good choice here . This is not simple local feedback as many think . It is usually a trans-impedance stage ( I in V out ) . If you every have tried to use a pre amp with a high output impedance you will know it is not the best idea you ever had . Especially if it almost matches the next stage ( higher can work ) . So why do people assume it is OK here ? I know the arguments and have to agree that many amps designed this way are fine . I just suspect what I have done here is worth a thought . Note 0R was the design goal . 47 R was to hand . It was the first time the 50 kHz distortion was better than perfect ( < 0.1 % ) .
4/ If class AB is mostly A then the application of feedback is easier . This amp will pump current as it then in class AB when loud . 8 mA will drive at least 3 sets of outputs on real music .
5 / I like long tail pair input as it makes life easy . Apart from that a single looks better . Such distortion as it as is harmless enough and invisible in this test .
6 / A complimentary feedback pair input for the very pedantic would be the optimum input . Very low distortion and noise . Slightly better stability . As I like double VAS I think LTP is a no brainer .
I am told that in 1938 Edward Turner by using a bit of thought managed to make a twin cylinder motorcycle for the price of a single , it saved the company . Although plenty of things were wrong with it ( balance factors , no centre support ) , it came to be the one to clone . I feel my amp I show although fundamentally excellent ( that is praise of it and not of myself ) is stupidly simple . A caprice . What I show previously in the MC1530 is better than 90% of what I see . How it accepts feedback especially . Well done J T .
Hopefully designing nice simple class A amps even I can understand.
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